U.S. patent application number 10/919036 was filed with the patent office on 2005-04-14 for method and apparatus for assigning scheduling for uplink packet transmission in a mobile communication system.
This patent application is currently assigned to SAMSUNG ELECTRONICS CO., LTD.. Invention is credited to Choi, Sung-Ho, Heo, Youn-Hyoung, Kim, Young-Bum, Kwak, Yong-Jun, Lee, Ju-Ho.
Application Number | 20050078651 10/919036 |
Document ID | / |
Family ID | 34067485 |
Filed Date | 2005-04-14 |
United States Patent
Application |
20050078651 |
Kind Code |
A1 |
Lee, Ju-Ho ; et al. |
April 14, 2005 |
Method and apparatus for assigning scheduling for uplink packet
transmission in a mobile communication system
Abstract
A method in a UE of transmitting buffer state information and
CSI for scheduling an uplink packet data service in a mobile
communication system supporting the uplink packet data service is
provided. The buffer state information indicates a state of a data
buffer for storing packet data to be transmitted from the UE and
the CSI indicates an uplink transmit power of the UE. The UE
acquires different transmission intervals of the buffer state
information and the CSI, initially transmits the buffer state
information and the CSI, if the amount of packet data stored in the
buffer is equal to or greater than a predetermined threshold, and
periodically transmits the buffer state information and the CSI at
the transmission intervals.
Inventors: |
Lee, Ju-Ho; (Suwon-si,
KR) ; Kwak, Yong-Jun; (Yongin-si, KR) ; Choi,
Sung-Ho; (Suwon-si, KR) ; Heo, Youn-Hyoung;
(Suwon-si, KR) ; Kim, Young-Bum; (Seoul,
KR) |
Correspondence
Address: |
DILWORTH & BARRESE, LLP
333 EARLE OVINGTON BLVD.
UNIONDALE
NY
11553
US
|
Assignee: |
SAMSUNG ELECTRONICS CO.,
LTD.
GYEONGGI-DO
KR
|
Family ID: |
34067485 |
Appl. No.: |
10/919036 |
Filed: |
August 16, 2004 |
Current U.S.
Class: |
370/349 |
Current CPC
Class: |
H04L 47/30 20130101;
H04W 52/14 20130101; H04W 52/40 20130101; H04W 52/362 20130101;
H04W 52/286 20130101; H04L 47/263 20130101; H04L 47/14 20130101;
H04W 72/1252 20130101; H04W 72/1284 20130101; H04W 28/14 20130101;
H04W 28/02 20130101; H04L 47/29 20130101; H04W 72/1231 20130101;
H04L 47/10 20130101 |
Class at
Publication: |
370/349 |
International
Class: |
H04B 007/00; H04J
003/24 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 16, 2003 |
KR |
2003-56733 |
Oct 1, 2003 |
KR |
2003-68506 |
Claims
What is claimed is:
1. A method in a user equipment (UE) for transmitting buffer state
information and channel state information (CSI) for scheduling an
uplink packet data service in a mobile communication system
supporting the uplink packet data service, the buffer state
information indicating a state of a data buffer for storing packet
data to be transmitted from the UE and the CSI indicating an uplink
transmit power of the UE, the method comprising the steps of:
acquiring different transmission intervals of the buffer state
information and the CSI; initially transmitting the buffer state
information and the CSI, if an amount of packet data stored in the
data buffer is at least equal to a predetermined threshold; and
periodically transmitting the buffer state information and the CSI
at the different transmission intervals.
2. The method of claim 1, further comprising the step of attaching
the buffer state information to a cyclic redundancy code (CRC) for
transmission error detection, before the initially transmitting and
the periodically transmitting steps.
3. The method of claim 1, wherein the buffer state information and
the CSI are initially transmitted and periodically transmitted in
assigned areas of a predetermined scheduling interval, and the
transmission intervals of the buffer state information and the CSI
are integer multiples of a duration of the predetermined scheduling
interval.
4. The method of claim 3, wherein the buffer state information and
the CSI are periodically transmitted in the assigned areas of
scheduling intervals from an initial transmission time, by integer
multiples of the predetermined transmission intervals.
5. The method of claim 3, wherein the buffer state information and
the CSI are periodically transmitted in the assigned areas of
scheduling intervals from predetermined reference scheduling
intervals for the buffer state information and the CSI, after an
initial transmission time, by integer multiples of the
predetermined transmission intervals.
6. The method of claim 5, wherein each of the reference scheduling
intervals is determined by
(CNT.sub.sch.sub..sub.--.sub.int-offset)mod(T/-
T.sub.sch.sub..sub.--.sub.int)=0 where
CNT.sub.sch.sub..sub.--.sub.int is an index of the reference
scheduling interval, offset is an integer value as different as
possible for each UE, mod is an operator that computes a remainder
of a division between two operands, T is a transmission interval of
the buffer state information or the CSI, and
T.sub.sch.sub..sub.--.sub.int is a duration of the scheduling
interval.
7. The method of claim 1, further comprising the step of
discontinuing the periodic transmission of the buffer state
information and the CSI, if the amount of the packet data stored in
the data buffer is less than the predetermined threshold.
8. The method of claim 1, further comprising the step of
discontinuing the periodic transmission of the buffer state
information and the CSI, upon receiving a scheduling release
message requesting termination of the transmission of the buffer
state information and the CSI.
9. The method of claim 1, wherein a transmission interval of the
buffer state information is longer than a CSI transmission
interval.
10. The method of claim 1, wherein when the UE communicates with at
least two Node Bs in a soft handover, a transmission interval of
the buffer state information is longer than a CSI transmission
interval.
11. The method of claim 1, wherein a transmission interval of the
buffer state information is shorter than a CSI transmission
interval.
12. The method of claim 1, wherein when the CSI reflects an uplink
channel state change over a term that is long enough to overcome
long-term fading, a transmission interval of the buffer state
information is shorter than a CSI transmission interval.
13. The method of claim 1, wherein the different transmission
intervals of the buffer state information and the CSI are
determined according to a quality of service (QoS) requirement for
the uplink packet data service and radio resources available to
receive the uplink packet data service.
14. A method in a Node B for receiving buffer state information and
channel state information (CSI) from a user equipment (UE) for
scheduling an uplink packet data service in a mobile communication
system supporting the uplink packet data service, comprising the
steps of: acquiring different reception intervals of the buffer
state information and the CSI; determining if the buffer state
information and the CSI have been initially received; and
periodically receiving the buffer state information and the CSI at
the different reception intervals, if the buffer state information
and the CSI have been initially received.
15. The method of claim 14, wherein the step of determining if the
buffer state information and the CSI have been initially received,
comprises the steps of: acquiring received data including the
buffer state information and a cyclic redundancy code (CRC) of the
received data for transmission error detection; and receiving the
buffer state information and the CSI, if the received data has no
error by a CRC check.
16. The method of claim 14, wherein the buffer state information
and the CSI are initially and periodically received in assigned
areas of a predetermined scheduling interval, and the different
reception intervals of the buffer state information and the CSI are
integer multiples of a duration of the predetermined scheduling
interval.
17. The method of claim 16, the buffer state information and the
CSI are periodically received in the assigned areas of scheduling
intervals from an initial reception time, by integer multiples of
the different reception intervals.
18. The method of claim 16, wherein the buffer state information
and the CSI are periodically received in the assigned areas of
scheduling intervals from predetermined reference scheduling
intervals for the buffer state information and the CSI, after an
initial reception time, by integer multiples of the different
reception intervals.
19. The method of claim 18, wherein each of the reference
scheduling intervals is determined by
(CNT.sub.sch.sub..sub.--.sub.int-offset
)mod(T/T.sub.sch.sub..sub.--.sub.int)=0 where
CNT.sub.sch.sub..sub.--.sub- .int it is an index of the reference
scheduling interval, offset is an integer as different as possible
for each UE, mod is an operator that computes a remainder of a
division between two operands, T is a reception interval of the
buffer state information or the CSI, and
T.sub.sch.sub..sub.--.sub.int is a duration of the scheduling
interval.
20. The method of claim 14, further comprising the steps of:
estimating the buffer state of the UE by calculating a difference
between previous buffer state information and an amount of packet
data received after the previous buffer state information; and
discontinuing the periodic reception of the buffer state
information and the CSI, if the buffer state estimate is less than
a predetermined threshold.
21. The method of claim 20, further comprising the step of
transmitting to the UE a scheduling release message requesting
termination of the transmission of the buffer state information and
the CSI.
22. The method of claim 14, wherein a reception interval of the
buffer state information is longer than a CSI reception
interval.
23. The method of claim 14, wherein when the UE communicates with
at least two Node Bs in a soft handover, a reception interval of
the buffer state information is longer than a CSI reception
interval.
24. The method of claim 14, wherein a reception interval of the
buffer state information is shorter than a CSI reception
interval.
25. The method of claim 14, wherein when the CSI reflects an uplink
channel state change over a long term enough to overcome long-term
fading, a reception interval of the buffer state information is
shorter than a CSI reception interval.
26. The method of claim 14, wherein the different reception
intervals of the buffer state information and the CSI are
determined according to a quality of service (QoS) requirement for
the uplink packet data service and radio resources available to the
Node B for the uplink packet data service.
27. A transmitter in a user equipment (UE) for transmitting buffer
state information and channel state information (CSI) for
scheduling an uplink packet data service in a mobile cornmunication
system supporting the uplink packet data service, the buffer state
information indicating a state of a data buffer for storing packet
data to be transmitted from the UE and the CSI indicating an uplink
transmit power of the UE, the transmitter comprising: a
transmission start and end decider for determining a transmission
start and end of the buffer state information and the CSI by
comparing an amount of packet data stored in the data buffer with a
predetermined threshold, the transmission start being determined as
a time when the data amount is at least equal to the predetermined
threshold; and a transmission time decider for acquiring different
transmission intervals of the buffer state information and the CSI,
and determining different transmission times for the buffer state
information and the CSI according to the acquired transmission
intervals, wherein the transmission start is used as a reference
time; a buffer state transmitter for periodically transmitting the
buffer state information at the buffer state transmission times;
and a CSI transmitter for periodically transmitting the CSI at the
CSI transmission times.
28. The transmitter of claim 27, wherein the buffer state
transmitter comprises: a switch for receiving the buffer state
information at each of the buffer state transmission time; a cyclic
redundancy code (CRC) adder for attaching a CRC to the buffer state
information in order to detect transmission errors from the buffer
station information; and a channel encoder for channel-encoding the
CRC-attached buffer state information and transmitting the
channel-encoded buffer state information.
29. The transmitter of claim 27, wherein the CSI transmitter
comprises: a switch for receiving the CSI at each of the CSI
transmission times; and a channel encoder for channel-encoding the
CSI and transmitting the channel-encoded CSI.
30. The transmitter of claim 27, wherein the buffer state
transmitter and the CSI transmitter transmit the buffer state
information and the CSI in assigned areas of a predetermined
scheduling interval, and the different transmission intervals of
the buffer state information and the CSI are integer multiples of a
duration of the scheduling interval.
31. The transmitter of claim 30, wherein the buffer state
transmitter and the CSI transmitter transmit the buffer state
information and the CSI in the assigned areas of scheduling
intervals from the reference time point, by integer multiples of
the different transmission intervals.
32. The transmitter of claim 30, wherein the buffer state
transmitter and the CSI transmitter transmit the buffer state
information and the CSI in the assigned areas of scheduling
intervals from predetermined reference scheduling intervals for the
buffer state information and the CSI, after the reference time, by
integer multiples of the different transmission intervals.
33. The transmitter of claim 32, wherein each of the reference
scheduling intervals is determined by
(CNT.sub.sch.sub..sub.--.sub.int-offset)mod(T/-
T.sub.sch.sub..sub.--.sub.int)=0 where
CNT.sub.sch.sub..sub.--.sub.int is an index of the reference
scheduling interval, offset is an integer as different as possible
for each UE, mod is an operator that computes a remainder of a
division between two operands, T is a transmission interval of the
buffer state information or the CSI, and
T.sub.sch.sub..sub.--.sub.int is a duration of the scheduling
interval.
34. The transmitter of claim 27, wherein the transmission time
decider determines the transmission end as a time when the amount
of the packet data stored in the data buffer is less than the
threshold.
35. The transmitter of claim 27, wherein the transmission time
decider determines the transmission end as a time when a scheduling
release message is received from the Node B, after the transmission
state time point, and the scheduling release message requests
termination of the transmission of the buffer state information and
the CSI.
36. The transmitter of claim 27, wherein a transmission interval of
the buffer state information is longer than a CSI transmission
interval.
37. The transmitter of claim 27, wherein when the UE communicates
with at least two Node Bs in a soft handover, a transmission
interval of the buffer state information is longer than a CSI
transmission interval.
38. The transmitter of claim 27, wherein a transmission interval of
the buffer state information is shorter than a CSI transmission
interval.
39. The transmitter of claim 27, wherein when the CSI reflects an
uplink channel state change over a term that is long enough to
overcome long-term fading, a transmission interval of the buffer
state information is shorter than a CSI transmission interval.
40. The transmitter of claim 27, wherein the different transmission
intervals of the buffer state information and the CSI are
determined according to a quality of service (QoS) requirement for
the uplink packet data service and radio resources available to
receive the uplink packet data service.
41. A receiver in a Node B for receiving buffer state information
and channel state information (CSI) from a user equipment (UE) for
scheduling an uplink packet data service in a mobile communication
system supporting the uplink packet data service, comprising: a
reception time decider for acquiring different reception intervals
of the buffer state information and the CSI, and determining
reception times for the buffer state information and the CSI
according to the different reception intervals using a reception
start time of the buffer state information and the CSI as a
reference time point; a buffer state receiver for determining if
the buffer state information has been initially received from the
UE, identifying a time when the buffer state information has been
initially received as the reception start time point, and
periodically receiving the buffer state information at the
determined buffer state reception times; and a CSI receiver for
periodically receiving the CSI at the determined CSI reception
times.
42. The receiver of claim 41, wherein the buffer state receiver
comprises: a switch for acquiring received data including the
buffer state information and a cyclic redundancy code (CRC) of the
received data for transmission error detection, continuously
receiving the received data before the reception start time point,
and receiving the received data at the determined buffer state
reception times after the reception start time point; and a CRC
checker for detecting the buffer state information from the
received data, if the received data has no error by a CRC
check.
43. The receiver of claim 41, wherein the CSI receiver comprises: a
switch for acquiring received data including the CSI at the
determined CSI reception times; and a channel decoder for decoding
the received data and detecting the CSI from the decoded data.
44. The receiver of claim 41, wherein the buffer state receiver and
the CSI receiver receive the buffer state information and the CSI
in assigned areas of a predetermined scheduling interval, and the
different reception intervals of the buffer state information and
the CSI are integer multiples of a duration of the predetermined
scheduling interval.
45. The receiver of claim 44, wherein the buffer state receiver and
the CSI receiver receive the buffer state information and the CSI
in the assigned areas of scheduling intervals from the reference
time, by integer multiples of the different reception
intervals.
46. The receiver of claim 44, wherein the buffer state receiver and
the CSI receiver receive the buffer state information and the CSI
in the assigned areas of scheduling intervals from predetermined
reference scheduling intervals for the buffer state information and
the CSI, after the reference time, by integer multiples of the
different reception intervals.
47. The receiver of claim 46, wherein each of the reference
scheduling intervals is determined by
(CNT.sub.sch.sub..sub.--.sub.int-offset
)mod(T/T.sub.sch.sub..sub.--.sub.int)=0 where
CNT.sub.sch.sub..sub.--.sub- .int is an index of the reference
scheduling interval, offset is an integer as different as possible
for each UE, mod is an operator that computes a remainder of a
division between two operands, T is a reception interval of the
buffer state information or the CSI, and
T.sub.sch.sub..sub.--.sub.int is a duration of the scheduling
interval.
48. The receiver of claim 41, wherein the reception time decider
estimates the buffer state of the UE by calculating a difference
between previous buffer state information and an amount of packet
data received after the previous buffer state information, and
determines a reception end time as a time when the buffer state
estimate is less than a predetermined threshold.
49. The receiver of claim 48, wherein the reception time decider
controls a scheduling release message to be transmitted to the UE
at the reception end time, and the scheduling release message
requests termination of the transmission of the buffer state
information and the CSI.
50. The receiver of claim 41, wherein a reception interval of the
buffer state information is longer than a CSI reception
interval.
51. The receiver of claim 41, wherein when the UE communicates with
at least two Node Bs in a soft handover, a reception interval of
the buffer state information is longer than a CSI reception
interval.
52. The receiver of claim 41, wherein a reception interval of the
buffer state information is shorter than a CSI reception
interval.
53. The receiver of claim 41, wherein when the CSI reflects an
uplink channel state change over a term that is long enough to
overcome long-term fading, a reception interval of the buffer state
information is shorter than a CSI reception interval.
54. The receiver of claim 41, wherein the different reception
intervals of the buffer state information and the CSI are
determined according to a quality of service (QoS) requirement for
the uplink packet data service and radio resources available to the
Node B for the uplink packet data service.
Description
PRIORITY
[0001] This application claims priority under 35 U.S.C. .sctn. 119
to applications entitled "Method and Apparatus for Assigning
Scheduling for Uplink Packet Transmission in a Mobile Communication
System" filed in the Korean Intellectual Property Office on Aug.
16, 2003 and assigned Ser. No. 2003-56733, and filed on Oct. 1,
2003 and assigned Ser. No. 2003-68506, the contents of which are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to a mobile
communication system, and in particular, to a method and apparatus
for efficiently transmitting and receiving scheduling assignment
information for uplink packet transmission.
[0004] 2. Description of the Related Art
[0005] An asynchronous WCDMA (Wideband Code Division Multiple
Access) communication system uses an EUDCH (Enhanced Uplink
Dedicated CHannel) to provide a high-rate packet data service on
the uplink. The EUDCH was proposed to improve the performance of
uplink packet transmission in asynchronous CDMA communication
systems. Besides the existing HSDPA (High Speed Downlink Packet
Access) schemes, AMC (Adaptive Modulation and Coding) and HARQ
(Hybrid Automatic Retransmission reQuest), the EUDCH technology
utilizes new techniques using a short TTI (Transmission Time
Interval). Also, Node B control scheduling is applied to uplink
channels. The Node B control scheduling of the uplink is very
different from downlink scheduling.
[0006] Orthogonality is not maintained between uplink signals from
a plurality of UEs (User Equipments). Therefore, the uplink signals
interfere with each other. As a Node B receives more uplink
signals, interference with an uplink signal from a particular UE
increases, thereby degrading the reception performance of the Node
B. Although the problem can be overcome by increasing the uplink
transmit power, the uplink signal with the increased transmit power
in turn interferes with other uplink signals. Therefore, the Node B
limits uplink signals that can be received with an acceptable
reception performance as shown in Equation (1),
ROT=I.sub.--0/N.sub.--0 (1)
[0007] where I.sub.--0 is the total receiving wideband power
spectral density of the Node B and N.sub.--0 is the thermal noise
power spectral density of the Node B. ROT represents uplink radio
resources available to Node B to receive the EUDCH packet data
service.
[0008] FIGS. 1A and 1B are graphs illustrating changes in uplink
radio resources available to the Node B. As illustrated in FIGS. 1A
and 1B, the uplink radio resources are the sum of ICI (Inter-Cell
Interference), voice traffic, and EUDCH packet traffic.
[0009] More specifically, FIG. 1A illustrates changes in a total
ROT when Node B control scheduling is not used. With no scheduling
of EUDCH packet traffic, a plurality of UEs may transmit data at
high rates and at the same time. In this case, the total ROT
exceeds a target ROT and the reception performance of the uplink
signals is degraded.
[0010] FIG. 1B illustrates changes in the total ROT when the Node B
control scheduling is used. The Node B control scheduling prevents
the UEs from transmitting data at high rates at the same time. When
a high rate is allowed for a particular UE, low rates are allowed
for other UEs, such that the total ROT does not exceed the target
ROT. As a result, the Node B control scheduling ensures a constant
reception performance all the time.
[0011] The Node B notifies UEs using the EUDCH when EUDCH data
transmission is available, or adjusts EUDCH data rates for them,
utilizing requested data rates or CSI (Channel State Information)
representing uplink quality from the UEs. In this Node control B
scheduling, the Node B assigns data rates to the UEs, such that the
total ROT does not exceed the target ROT in order to improve system
performance. The Node B can assign a low data rate to a remote (far
away) UE, and a high data rate to a nearby UE.
[0012] FIG. 2 illustrates the basic concept of the Node B control
scheduling of the EUDCH. Referring to FIG. 2, reference numeral 200
denotes a Node B supporting the EUDCH and reference numerals 210 to
216 denote UEs using the EUDCH. When the data rate of a UE
increases, the Node B receives data from the UE at an increased
reception power. Therefore, the ROT of the UE contributes more to
the total ROT. If the data rate of another UE decreases, the Node B
receives data from the UE at a decreased reception power.
Therefore, the ROT of the UE contributes less to the total ROT. The
Node B schedules the EUDCH packet data considering the relationship
between data rates and radio resources and UEs-requested data
rates.
[0013] In FIG. 2, the UEs 210 to 216 transmit packet data at
different uplink transmit power levels according to the distances
between them and the Node B 200. The farthest UE 210 transmits
packet data at the highest uplink transmit power level 220, while
the nearest UE 214 transmits packet data at the lowest uplink
transmit power level 224. The Node B schedules uplink data
transmission in the manner that makes the transmit power of the
uplink channel is inversely proportional to its data rate in order
to improve system performance, while maintaining the total ROT and
reducing ICI. Therefore, the Node B assigns a relatively low data
rate to the UE 210 having the highest transmit power and a relative
high data rate to the UE 214 having the lowest transmit power.
[0014] FIG. 3 illustrates an operation for assigning a data rate
for EUDCH packet transmission and transmitting packet data at the
assigned data rate in a UE. Referring to FIG. 3, an EUDCH is
established between a Node B 300 and a UE 302 in step 310. Step 310
involves transmission and reception of messages on dedicated
transport channels. In step 312, the UE 302 notifies the Node B 300
of a desired data rate and uplink CSI. The uplink CSI includes the
uplink transmit power and/or transmit power margin of the UE.
[0015] The Node B 300 estimates the uplink channel state by
comparing the uplink transmit power with uplink received power. If
the difference between the uplink transmit power and the uplink
received power is small, the uplink channel state is good. If the
difference is large, the uplink channel state is bad. When the UE
transmits only the transmit power margin, the Node B 300 estimates
the uplink transmit power by subtracting the transmit power margin
from a known maximum available transmit power of the UE 302. The
Node B 300 determines a maximum available data rate for the UE
based on the estimated uplink channel state and the requested data
rate.
[0016] In step 314, the Node B 300 notifies the UE 302 of the
maximum data rate by scheduling assignment information. The UE 302
selects a data rate equal to or less than the maximum data rate and
transmits packet data at the selected data rate to the Node B 300
in step 316.
[0017] To transmit all packet data of an EUDCH data buffer to the
Node B 300, the UE 302 must receive the scheduling assignment
information from the Node B 300 at every predetermined interval. If
the UE 302 transmits buffer status information and CSI at every
scheduling interval, the resulting signaling overhead decreases the
efficiency of uplink packet transmission. Therefore, there is a
need for an efficient scheduling scheme to prevent the uplink
signaling overhead.
SUMMARY OF THE INVENTION
[0018] Therefore, the present invention has been designed to
substantially solve at least the above problems and/or
disadvantages and to provide at least the advantages below.
Accordingly, an object of the present invention is to provide a
method and apparatus for reducing uplink signaling overhead in
uplink packet transmission.
[0019] Another object of the present invention is to provide a
method and apparatus for controlling the transmission intervals of
buffer status information and CSI on the uplink to reduce signaling
overhead.
[0020] A further object of the present invention is to provide a
method and apparatus for efficiently transmitting uplink packets by
controlling the transmission intervals of buffer status information
and CSI.
[0021] Still another object of the present invention is to provide
a method and apparatus for efficiently utilizing radio resources by
controlling the transmission intervals of buffer status information
and CSI.
[0022] The above and other objects are achieved by providing a
method of transmitting and receiving buffer state information and
CSI for scheduling of an uplink packet data service in a mobile
communication system.
[0023] According to an aspect of the present invention, in a method
in a UE of transmitting buffer state information and CSI for
scheduling of an uplink packet data service in a mobile
communication system supporting the uplink packet data service, the
UE acquires different transmission intervals of the buffer state
information and the CSI, initially transmits the buffer state
information and the CSI if the amount of packet data stored in a
buffer is equal to or greater than a predetermined threshold, and
periodically transmits the buffer state information and the CSI at
the transmission intervals.
[0024] According to another aspect of the present invention, in a
method in a Node B of receiving buffer state information and CSI
from a UE for scheduling of an uplink packet data service in a
mobile communication system supporting the uplink packet data
service, the Node B acquires different reception intervals of the
buffer state information and the CSI, determines if the buffer
state information and the CSI have been initially received, and
periodically receives the buffer state information and the CSI at
the reception intervals, if the buffer state information and the
CSI have been initially received.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The above and other objects, features, and advantages of the
present invention will become more apparent from the following
detailed description when taken in conjunction with the
accompanying drawings in which:
[0026] FIG. 1A illustrates changes in the uplink radio resources of
a Node B in the case where Node B control scheduling is not
used;
[0027] FIG. 1B illustrates changes in the uplink radio resources of
the Node B in the case where the Node B control scheduling is
used;
[0028] FIG. 2 illustrates the Node B and UEs in an uplink packet
transmission;
[0029] FIG. 3 illustrates information exchanged for uplink packet
transmission between the Node B and a UE;
[0030] FIG. 4 is a block diagram of a UE transmitter for
transmitting uplink packets;
[0031] FIGS. 5A and SB respectively illustrate the structure of a
scheduling control channel (EU-SCHCCH) for receiving uplink packets
and the structure of an EU-SCHCCH transmitter in the Node B;
[0032] FIG. 6 illustrates continuous transmission of buffer status
information and CSI by which Node B control scheduling is carried
out;
[0033] FIG. 7 illustrates an uplink power control operation of a UE
in a soft handover region;
[0034] FIG. 8 is a flowchart illustrating a method for setting a
CSI transmission interval according to an embodiment of the present
invention;
[0035] FIG. 9 illustrates the format of buffer status information
and CSI transmitted from a UE according to an embodiment of the
present invention;
[0036] FIG. 10 illustrates an embodiment of transmission of the
buffer status information and CSI according to the present
invention;
[0037] FIG. 11 illustrates another embodiment of transmission of
the buffer status information and CSI according to the present
invention;
[0038] FIG. 12 is a block diagram of an EUDCH transmission
controller for transmitting the buffer status information and CSI
according to an embodiment of the present invention;
[0039] FIG. 13 is a flowchart illustrating a method in a UE for
transmitting the buffer status information and CSI according to an
embodiment of the present invention;
[0040] FIG. 14 is a block diagram of an EUDCH receiver in a Node B
for receiving the buffer status information and CSI according to an
embodiment of the present invention;
[0041] FIG. 15 is a flowchart illustrating a method in the Node B
for receiving the buffer status information and CSI according to
the embodiment of the present invention;
[0042] FIG. 16 is a block diagram of an EU-SCHCCH receiver in the
UE for receiving scheduling assignment information according to an
embodiment of the present invention; and
[0043] FIG. 17 is a flowchart illustrating an operation in the UE
for receiving the scheduling assignment information according to an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0044] Preferred embodiments of the present invention will be
described in detail herein below with reference to the accompanying
drawings. In the following description, well-known functions or
constructions are not described in detail because they would
obscure the invention in unnecessary detail.
[0045] In accordance with the present invention, for a Node B to
control scheduling of the EUDCH used for high-speed uplink packet
data service, different transmission intervals are set for
transmitting buffer status information and CSI from a UE. The UE
transmits buffer status information and CSI to the Node B at the
transmission intervals. An RNC (Radio Network Controller) that
controls the radio resources of the Node B sets the transmission
intervals of the buffer status information and CSI, taking into
account a QoS (Quality of Service) requirement for the EUDCH
service, the ROT of the uplink, and a handover situation or a
normal situation of the UE.
[0046] FIG. 4 is a block diagram of a transmitter in a UE
supporting the EUDCH service. Uplink physical channels available to
the UE are a DPDCH (Dedicated Physical Data Channel), an EU-DPDCH,
which is a DPDCH used for the EUDCH service, a DPCCH (Dedicated
Physical Control Channel), an HS-DPCCH (High Speed DPCCH) for HSDPA
service, and an EU-DPCCH that is a DPCCH used for the EUDCH
service.
[0047] The EU-DPCCH delivers the buffer status information and CSI
of a UE. The CSI includes an uplink transmit power and an uplink
transmit power margin required for a Node B to estimate the uplink
channel state of the UE. Also, the EU-DPCCH delivers an E-TFRI
(EUDCH-Transport Format and Resource Indicator) representing the
transport format of the EU-DPDCH including the used data size, data
rate, and modulation scheme. The EU-DPDCH conveys packet data at a
data rate that is determined according to scheduling assignment
information received from the Node B. While the DPDCH only supports
BPSK (Binary Phase Shift Keying), the EU-DPDCH can support
higher-order modulations such as QPSK (Quadrature Phase Shift
Keying) and 8PSK (8-ary PSK) and BPSK, to increase data rate while
maintaining the number of simultaneous spreading codes.
[0048] Referring to FIG. 4, an EUDCH transmission controller 404
monitors an EUDCH data buffer 400 having data to be transmitted on
the EUDCH, and acquires buffer status information required for Node
B control scheduling. Also, the EUDCH transmission controller 404
acquires CSI from an uplink transmission path (not shown). The
EUDCH transmission controller 404 determines an E-TFRI representing
the transport format of EUDCH packet data. The E-TFRI is determined
according to a maximum data rate allowed by a scheduling assigner
402. The EUDCH transmission controller 404 generates EU-DPCCH data
including the buffer status information, CSI, and E-TFRI, and
outputs it to a spreader 408.
[0049] DPDCH data is spread at a chip rate with an OVSF (Orthogonal
Variable Spreading Factor) code c.sub.d assigned to the DPDCH in a
spreader 422, multiplied by a channel gain .beta..sub.d in a gain
adjuster 424, and applied to the input of a summer 426. The
EU-DPCCH data is spread at a chip rate with an OVSF code c.sub.c,eu
assigned to the EU-DPCCH in the spreader 408, multiplied by a
channel gain .beta..sub.c,eu in a gain adjuster 410, and applied to
the input of the summer 426. The summer 426 sums the outputs of the
gain adjusters 424 and 410, and transmits the sum to a summer 420,
which assigns the sum to an I channel.
[0050] An EUDCH packet transmitter 406 reads as much packet data as
indicated by the E-TFRI from the EUDCH data buffer 400 and encodes
the packet data according to the E-TFRI, thereby producing EU-DPDCH
data. A modulation mapper 412 modulates the EU-DPDCH data in BPSK,
QPSK, or 8PSK, and outputs an EU-DPDCH modulation symbol sequence.
BPSK modulation symbols have real number values, whereas QPSK or
8PSK modulation symbols have complex number values. It should be
noted that the following description is made in the context of
using QPSK or 8PSK for the EU-DPDCH.
[0051] The modulation mapper 412 converts the EU-DPDCH data to a
complex symbol sequence. A spreader 414 spreads the modulation
symbol sequence at a chip rate with an OVSF code c.sub.d,eu
assigned to the EU-DPDCH. The spread EU-DPDCH signal is multiplied
by a channel gain .beta..sub.d,eu in a gain adjuster 418 and
applied to the input of the summer 420.
[0052] DPCCH data, which is control information of the DPDCH, is
spread at a chip rate with an OVSF code c.sub.c assigned to the
DPCCH in a spreader 428, multiplied by a channel gain .beta..sub.c
in a gain adjuster 430, and applied to the input of a summer 436.
HS-DPCCH data, which is control information for an HSDPA service,
is spread at a chip rate with an OVSF code c.sub.HS assigned to the
HS-DPCCH in a spreader 432, multiplied by a channel gain
.beta..sub.HS in a gain adjuster 434, and applied to the input of
the summer 436. The summer 436 sums the outputs of the gain
adjusters 430 and 434, and transmits the sum to a phase adjuster
438, which assigns the sum to a Q channel.
[0053] The summer 420 sums the outputs of the summer 426, the gain
adjuster 418, and the phase adjuster 438, and outputs the resulting
complex symbol sequence to a scrambler 442. The scrambler 442
scrambles the complex symbol sequence with a scrambling code
S.sub.dpch,n. The scrambled complex symbol sequence is converted to
pulse form in a pulse shaping filter 444 and transmitted to the
Node B through an RF (Radio Frequency) processor 446 and an antenna
448.
[0054] FIG. 5A illustrates a format of the EU-SCHCCH for delivering
EUDCH scheduling assignment information, and FIG. SB is a block
diagram of an EU-SCHCCH SCHCCH transmitter. The EU-SCHCCH delivers
scheduling assignment information 500 including Scheduling
Grant/Release Messages and allowed maximum data rates to a
plurality of UEs, using one OVSF code. A Scheduling Grant/Release
Message indicates if the EUDCH packet data is transmitted. The
scheduling assignment information 500 includes the IDs of the UEs
for which the Scheduling Grant/Release Messages and the allowed
maximum data rates are destined.
[0055] A serial-to-parallel converter 510 converts the EU-SCHCCH
data containing the scheduling assignment information 500 to
parallel symbol sequences in. A modulation mapper 512 converts the
parallel symbol sequences to I and Q streams. Spreaders 514 and 516
spread the I and Q streams, respectively, with an OVSF code
assigned to the EU-SHCCH, C.sub.sch.sub..sub.--.sub.cont at a chip
rate. A phase adjuster 518 multiplies the Q stream received from
the spreader 516 by a phase variation j. A summer 520 sums the
outputs of the spreader 514 and the phase adjuster 518. A scrambler
522 scrambles the complex symbol sequence received from the summer
520 with a scrambling code S.sub.sch,cont The scrambled complex
symbol sequence is converted to pulse form in a pulse shaping
filter 524 and transmitted to the UEs through an RF processor 526
and an antenna 528.
[0056] FIG. 6 illustrates a continuous transmission of buffer
status information and CSI from a UE to a Node B, and transmission
of scheduling assignment information from the Node B to the UE in a
conventional EUDCH system. The UE transmits to the Node B the
buffer status information and CSI at every predetermined interval
(i.e., scheduling interval T.sub.sch.sub..sub.--.sub.int) to
receive the scheduling assignment information.
[0057] Referring to FIG. 6, packet data destined for the Node B is
stored (generated) in the EUDCH data buffer of the UE at a time
600. For a time period 602, the UE transmits to the Node B buffer
status information indicating the data amount of the data buffer
and CSI, representing an uplink transmit power and a transmit power
margin. The Node B determines a maximum data rate for the UE based
on the buffer status information and CSI, and transmits the maximum
data rate to the UE by scheduling assignment information for a time
period 610.
[0058] When all the packet data stored in the EUDCH data buffer
cannot be transmitted to the Node B at one time, the UE
continuously transmits the buffer status information and CSI at the
scheduling interval T.sub.sch.sub..sub.--.sub.int from the time
period 602 through a time 606, in order to request scheduling
assignment to the Node B. The packet data is completely transmitted
to the Node B by the time 606. Therefore, after time 606, the UE
discontinues transmission of the buffer status information and CSI.
The Node B, although receiving the buffer status information and
CSI from the UE, does not transmit the scheduling assignment
information for a time period 612 if an ROT condition is not
satisfied.
[0059] Therefore, the transmission of the buffer status information
and CSI at every scheduling interval significantly increases uplink
overhead and reduces uplink traffic capacity. Accordingly, in a
preferred embodiment of the present invention, different
transmission intervals are set for the buffer status information
and the CSI. The reasons for setting the different transmission
intervals will be described in more detail herein below.
[0060] First, from the perspective of uplink power control,
transmission of the buffer status information and the CSI at
different transmission intervals will be described.
[0061] The Node B continuously measures the strength of an uplink
signal received from the UE and transmits a UL TPC (Uplink Transmit
Power Control) command to the UE according to the measurement. If
the TPC command indicates a power decrease, the UE decreases its
uplink transmit power. If the TPC command indicates a power
increase, the UE increases the uplink transmit power. Therefore,
for a non-CSI reception period, the Node B can estimate the
transmit power of the UE by Equation (2),
Transmit_power_est=CSI_prev+power_control_step_size.times.(up_count_down_c-
ount) (2)
[0062] where Transmit_power_est is an estimate of the transmit
power of the UE, CSI_prev is previously received information about
the UE's transmit power, up_count is the number of power increase
commands after receiving CSI_prev, and down_count is the number of
power decrease commands after receiving CSL_prev.
power_control_step_size is an increment/decrement unit of the
transmit power in relation to a power increase/decrease command. As
noted from Equation (2), the Node B estimates the current transmit
power of the UE using the previous transmit power of the UE and the
TPC commands transmitted by the Node B. However, when the UE is
located in a soft handover region, Equation (2) is not valid. This
will be described in more detail with reference to FIG. 7.
[0063] FIG. 7 illustrates an uplink power control operation of a UE
in a soft handover region. Referring to FIG. 7, a UE 720 is located
in a soft handover region and transmits data to at least two active
Node Bs (three active Node Bs 710, 712, and 714, herein). The
active Node Bs 710, 712, and 714 demodulate the received data and
transmit the demodulated data to an RNC 700. This scheme enables an
active Node B that demodulates the data without errors among the
Node Bs 710, 712, and 714 to transmit the demodulated data to the
RNC 700, thereby achieving a macro selection diversity gain.
[0064] The UE 720 receives three downlink TPC commands from the
active Node Bs 710, 712, and 714. If at least one of the TPC
commands indicates a power decrease, the UE 720 decreases its
transmit power. If all of the TPC commands indicate a power
increase, the UE 720 increases the transmit power.
[0065] However, because each active Node B has no knowledge of TPC
commands from the other active Node Bs, the transmit power of the
UE 720 estimated by the active Node B using Equation (2) is
different from the actual transmit power of the UE 720. Therefore,
the UE 720 must have a shorter CSI transmission interval in order
for the active Node Bs 710, 712, and 714 to accurately detect the
transmit power of the UE 720 in the soft handover region.
[0066] When the UE does not report its buffer status, the Node B
estimates the current buffer status of the UE utilizing the
previous reported buffer status by Equation (3),
Buffer_state_est=Buffer_state prev-Data_sent (3)
[0067] where Buffer_state_est is an estimate of the current buffer
status, Buffer_state_prev is the previous received buffer status
value, and Data_sent is the amount of data received from the UE
after receiving Buffer_state_prev, acquired using an E-TFRI
received from the UE. Because the E-TFRI represents the data size,
coding rate, and modulation scheme of EU-DPDCH data, the Node B can
determine the amount of data received from the UE by the data size.
The E-TFRI is typically set to have a lower error rate than the TPC
command in order to improve the reception performance of the packet
data. Therefore, the estimate of the buffer status is relatively
reliable compared to the transmit power estimate. Accordingly, the
transmission interval of the buffer status information is longer
than the CSI transmission interval.
[0068] FIG. 8 is a flowchart illustrating a method for setting the
transmission intervals of buffer status information and CSI in an
RNC according to an embodiment of the present invention. Referring
to FIG. 8, the RNC determines a buffer status transmission interval
T.sub.buffer for a UE requesting an EUDCH service, considering an
ROT condition and a QoS requirement for the EUDCH service in step
800. The ROT condition is a condition that a measured ROT should
not exceed a target ROT. In step 802, the RNC determines if the UE
is in a handover region. If the UE is in the handover region, the
RNC proceeds to step 804. If the UE is not in the handover region,
the RNC proceeds to step 806.
[0069] In step 804, the RNC sets a CSI transmission interval
T.sub.CSI for the UE to be equal to T.sub.sch,int. In step 806, the
RNC calculates T.sub.CSI by Equation (4),
[0070] T.sub.CSI=.left
brkt-bot.(P.sub.e,E-TFRI/P.sub.e,TPC).times.T.sub- .buffer (4)
[0071] where .left brkt-bot.A.left brkt-bot. is a function of
obtaining a maximum integer equal to or less than A, P.sub.e,E-TRI
is a reception error rate requirement for the E-TFRI, and
P.sub.e,TPC is a reception error rate requirement. for a TPC
command transmitted to the UE. As noted from Equation (4),
T.sub.CSI is set to be shorter than T.sub.buffer according to the
reception error rates of the E-TFRI and the TPC command. The RNC
transmits T.sub.buffer and T.sub.CSI to the UE by an RRC (Radio
Resource Control) signaling message and to the Node B by an NBAP
(Node B Application Part) signaling message.
[0072] In the above-described case, T.sub.buffer is longer than
T.sub.CSI. However, considering the fact that a fading-caused
temporary channel change is overcome to a considerable extent
through power control in CDMA systems, the Node B control
scheduling can be performed by taking into account long-term fading
such as topographical features-incurred shadowing, that is, an
average channel change over a long term. In this case, the average
channel state over a long term is reflected in the CSI. As a
result, T.sub.CSI can be set to be longer than T.sub.buffer.
[0073] When T.sub.CSI is shorter than T.sub.buffer and T.sub.CSI is
longer than T.sub.buffer have been described above. However, the
present invention is not limited to those cases and it is to be
appreciated that the T.sub.CSI is different from T.sub.buffer under
certain circumstances.
[0074] An operation and a system structure for transmitting buffer
status information and CSI at the different transmission intervals,
when t.sub.CSI and t.sub.buffer are set to be different, will now
be detailed below.
[0075] FIG. 9 illustrates a format of buffer status information and
CSI transmitted from a UE according to an embodiment of the present
invention. Referring to FIG. 9, the buffer status information and
CSI are transmitted in one scheduling interval. The scheduling
interval is 10 ms in duration. To set different transmission
intervals for the buffer status information and the CSI, the UE
channel-encodes the buffer status information and the CSI through
different coding chains. That is, the buffer status information is
attached with CRC (Cyclic Redundancy Check) bits and then
channel-encoded, whereas the CSI is directly channel-encoded
without attachment of CRC bits. The Node B determines that the
buffer status information has been received by a CRC check. Because
the CSI follows the buffer status information, a decision as to
whether or not the CSI has been received depends on whether or not
the buffer status information has been received.
[0076] In accordance with an embodiment of the present invention,
the UE preferably operates as follows:
[0077] (1) If an amount of packet data stored in an EUDCH data
buffer is equal to or greater than a predetermined scheduling
threshold, a UE starts to transmit buffer status information and
CSI to a Node B;
[0078] (2) The UE repeatedly transmits buffer status information
and a CSI at every predetermined transmission interval of which an
RNC has notified a UE. As described above, the buffer status
information and the CSI are transmitted at different intervals;
and
[0079] (3) If an amount of packet data stored in the EUDCH data
buffer is reduced below the threshold, the UE discontinues
transmission of the buffer status information and the CSI. Also,
when receiving from the Node B a Scheduling Release message
indicating termination of the Node B control scheduling, the UE
discontinues transmission of the buffer status information and the
CSI.
[0080] The Node B operates as follows:
[0081] (1) The Node B continuously CRC-checks the EU-DPCCH to
determine whether buffer status information has been received from
the UE. Upon detecting the buffer status information in a
scheduling interval, the Node B receives the CSI following the
buffer status information in the same scheduling interval;
[0082] (2) Once the Node B has initially received the buffer status
information and the CSI, it repeatedly receives them in scheduling
intervals determined according to the predetermined reception
intervals that the RNC told the Node B. As described above, the
Node B receives the buffer status information and the CSI at
different reception intervals. The Node B then generates scheduling
assignment information based on the buffer status information and
the CSI;
[0083] (3) The Node B estimates the amount of packet data stored in
the EUDCH data buffer of the UE by Equation (3), and if the
estimate is less than the predetermined threshold, discontinues
reception of the buffer status and the CSI, and
[0084] (4) In another case, in order to command the UE to
discontinue transmission of the buffer status information and the
CSI, the Node B transmits the Scheduling Release message to the
UE.
[0085] FIG. 10 illustrates an embodiment of EU-DPCCH signaling for
scheduling assignment between the UE and the Node B according to
the present invention. CNT.sub.sch.sub..sub.--.sub.int denotes an
index of a scheduling interval. Each scheduling interval is divided
into a buffer status information part and a CSI part.
[0086] In a scheduling interval 1010 with
CNT.sub.sch.sub..sub.--.sub.int=- 10, the UE initially transmits
buffer status information and CSI to the Node B, when determining
that the amount of packet data stored in the EUDCH data buffer is
equal to or greater than a scheduling threshold. The UE
periodically transmits the buffer status information and the CSI at
their respective transmission intervals. The transmission interval
of the buffer status information is eight times the scheduling
interval T.sub.sch.sub..sub.--.sub.int. Therefore, the buffer
status information is transmitted in scheduling intervals 1010,
1014, and 1018 with CNT.sub.sch.sub..sub.--.sub.int=10 18, and 26.
The transmission interval of the CSI is four times the scheduling
interval T.sub.sch.sub..sub.--.su- b.int. Therefore, the CSI is
transmitted in scheduling intervals 1010, 1012, 1014, 1016, and
1018 with CNT.sub.sch.sub..sub.--.sub.int=10, 14, 18, 22, and
26.
[0087] After initially receiving the buffer status information and
the CSI, the Node B receives them periodically at the reception
intervals of which the RNC has notified the Node B. In time periods
1000 and 1002, the Node B determines scheduling assignment
information based on the last buffer status information and CSI and
the current ROT, and transmits it to the UE.
[0088] The Node B estimates the amount of data stored in the EUDCH
data buffer of the UE using Equation (3) and, if determining that
the UE has completely transmitted the packet data from the EUDCH
data buffer, discontinues transmission of the scheduling assignment
information to the UE. The Node B can transmit a Scheduling Release
message to the UE in a time period 1004, notifying termination of
transmission of the scheduling assignment information to the UE.
Upon receiving the Scheduling Release message, the UE terminates
transmission of the buffer status information and the CSI. To
determine if new buffer status information has been received from
the UE after the termination of the scheduling, the Node B
continuously CRC-checks the EU-DPCCH in each scheduling interval.
When the Node B does not use a Scheduling Grant message, the UE
discontinues the transmission of the buffer status information, and
the CSI when the amount of the packet data stored in the EUDCH data
buffer is less than the threshold.
[0089] As illustrated in FIG. 10, the periodic transmission of the
buffer status information and CSI starts from the first
transmission of the buffer status information. It can be further
contemplated as another embodiment of the present invention that
the transmission time points of the buffer status information and
CSI are determined irrespective of the first transmission time
point of the buffer status information. The transmission time
points of the buffer status information and CSI are calculated by
Equation (5) and Equation (6), respectively,
(CNT.sub.sch.sub..sub.--.sub.int-offset_buffer)mod(T_buffer/T.sub.sch.sub.-
.sub.--.sub.int)=0 (5)
(CNT.sub.sch.sub..sub.--.sub.int-offest.sub.--CSI)mod(T.sub.--CSI/T.sub.sc-
h.sub..sub.--.sub.int)=0 (6)
[0090] where mod is an operator that computes the remainder of the
division between two operands, CNT.sub.sch.sub..sub.--.sub.int is a
scheduling interval index, and offset.sub.--buffer is an integer
specific to each UE to prevent a plurality of UEs from providing
the EUDCH service from transmitting buffer status information at
the same time, thereby increasing the measured ROT of the Node B.
Each UE transmits the buffer status information to the Node B in
scheduling intervals satisfying Equation (5) according to its
offset_buffer. Similarly, offset_CSI is an integer specific to each
UE to prevent the UEs from transmitting CSIs at the same time, thus
increasing the measured ROT of the Node B. Each UE transmits the
CSI to the Node B in scheduling intervals satisfying Equation (6)
according to its offset_CSI. Additionally, offset_buffer and
offset_CSI can be identical or different.
[0091] FIG. 11 illustrates another embodiment of transmission of
the buffer status information and CSI according to the present
invention. Referring to FIG. 11, the UE has offset_buffer set to 0
and offset_CSI set to 0. T.sub.buffer is eight times
T.sub.sch.sub..sub.--.sub.int, and t.sub.CSI is four times
T.sub.sch.sub..sub.--.sub.int. According to Equation (5), the
buffer status information is transmitted in scheduling intervals
1106 and 1108 with CNT.sub.sch.sub..sub.--.sub.INT=16 and 24.
According to Equation (6), the CSI is transmitted in scheduling
intervals 1105, 1106, 1107, 1108, and 1109 with
CNT.sub.sch.sub..sub.--.sub.INT=12, 16, 20, 24, and 28. After
initially transmitting the buffer status information and the CSI in
a scheduling interval 1104, the UE transmits the CSI in the
scheduling intervals 1105, 1106, 1107, 1108, and 1109 and the
buffer status information in the scheduling intervals 1106 and
1108.
[0092] FIG. 12 is a block diagram of an EUDCH transmission
controller 1200 according to an embodiment of the present
invention. Referring to FIG. 12, a transmission start and end
decider 1202 determines the start and end of transmission of buffer
status information and CSI. The transmission start is determined by
comparing input buffer status information with a predetermined
threshold. If the buffer status information indicating the amount
of packet data stored in the EUDCH data buffer is equal to or
greater than the threshold, the transmission start and end decider
1202 outputs a start signal, considering that it is time to start
to transmit the buffer status information and the CSI. The end is a
time point when a Scheduling Release message is received from the
Node B. Alternatively, when the buffer status information is less
than the threshold, the transmission start and end decider 1202
outputs an end signal, considering that it is time to terminate the
transmission of the buffer status information and the CSI.
[0093] A transmission time decider 1204, upon receiving the start
signal from the transmission start and end decider 102, determines
the transmission time points of the buffer status information and
CSI. The transmission time points are represented by
CNT.sub.sch.sub..sub.--.sub.i- nt as illustrated in FIGS. 10 and
11. The RNC notifies the transmission time decider 1204 of
t.sub.buffer and T.sub.CSI by upper layer signaling. When the
transmission time points of the buffer status information are
determined, the transmission time decider 1204 activates a buffer
status switch 1206 in the scheduling intervals corresponding to the
determined transmission time points. When the transmission time
points of the CSI are determined, the transmission time decider
1204 activates a CSI switch 1214 in the scheduling intervals
corresponding to the determined transmission time points.
[0094] The buffer status switch 1206 switches the buffer status
information to a CRC adder 1208. The buffer status information is
attached with CRC bits in the CRC adder 1208 and channel-encoded in
a channel encoder 1210. The channel-coded buffer status information
is applied to the input of a multiplexer (MUX) 1212. The CSI switch
1214 switches the CSI to a channel encoder 1216. The CSI is
channel-encoded in the channel encoder 1216 and input to the MUX
1212. An EUDCH TF (Transport Format) decider 1218 determines the
transport format of packet data for the EUDCH service based on
scheduling assignment information received from the Node B and
generates an E-TFRI representing the decided transport format. The
E-TFRI is added with CRC bits in a CRC adder 1220 and
channel-encoded in a channel encoder 1222. The channel-coded E-TFRI
is input to the MUX 1212. The MUX 1212 multiplexes the coded buffer
status information, CSI, and E-TFRI, and transmits the multiplexed
signal on the EU-DPCCH.
[0095] An EUDCH packet transmitter 1224 transmits the packet data
stored in the EUDCH data buffer using the transport format
determined by the EUDCH TF decider 1218.
[0096] FIG. 13 is a flowchart illustrating an operation of a UE
transmitter according to an embodiment of the present invention.
Referring to FIG. 13, the UE monitors its buffer status, that is,
the amount of data stored in the EUDCH data buffer in step 1300 and
determines whether the data amount is equal to or greater than the
threshold THRES.sub.buffer in step 1302. If the data amount is
equal to or greater than THRES.sub.buffer, the UE proceeds to step
1306. If the data amount is less than THRES.sub.buffer, the UE
proceeds to step 1304. In step 1304, the UE waits until a next
scheduling interval, and returns to step 1300 to monitor the EUDCH
data buffer.
[0097] In step 1306, the UE transmits buffer status information and
CSI to the Node B. It waits until the next scheduling interval in
step 1308 and monitors the EUDCH data buffer in step 1310. In step
1312, the UE determines whether to continue transmitting the buffer
status information and CSI. The determination is made by comparing
the amount of packet data stored in the EUDCH data buffer with
THRES.sub.buffer. If the data amount is still equal to or greater
than THRES.sub.buffer, the UE proceeds to step 1314 to continue
transmitting the buffer status information and the CSI. If the data
amount is less than THRES.sub.buffer, the UE proceeds to step 1322.
In step 1322, the UE determines whether to continue the EUDCH data
service. If the UE determines to continue the EUDCH data service,
it waits until the next scheduling interval in step 1324. However,
if the UE determines not to continue the EUDCH data service, it
terminates the procedure.
[0098] In step 1314, the UE determines whether it is time to
transmit the buffer status information by comparing the index of
the current scheduling interval with the transmission time points
of the buffer status information. The transmission time points are
determined according to the transmission interval of the buffer
status information, which the RNC notified the UE of. If it is time
to transmit the buffer status information, the UE proceeds to step
1316. Otherwise, the UE proceeds to step 1318. The UE transmits the
buffer status information in step 1316 and proceeds to step
1318.
[0099] In step 1318, the UE determines whether it is time to
transmit the CSI by comparing the index of the current scheduling
interval with the transmission time points of the CSI. The
transmission time points are determined according to the
transmission interval of the CSI, which the RNC notified the UE of.
If the current scheduling index is identical to a transmission time
point of the CSI, the UE proceeds to step 1320. However, if the
current scheduling index is not identical to a transmission time
point of the CSI, the UE returns to step 1308. The UE transmits the
CSI in step 1320 and returns to step 1308.
[0100] FIG. 14 is a block diagram of a Node B receiver according to
an embodiment of the present invention. Referring to FIG. 14, an
antenna 1400 receives an RF signal from the UE. An RF processor
1402 downconverts the RF signal to a baseband signal. A pulse
shaping filter 1404 converts the baseband signal to a digital
signal. A descrambler 1406 descrambles the digital signal with the
scrambling code C.sub.scramble. The descrambled signal is
multiplied by the OVSF code C.sub.OVSF in a despreader 1408 and
transmitted to a demultiplexer (DEMUX) 1412 through a channel
compensator 1410. The DEMUX 1412 demultiplexes a signal received
from the channel compensator 1410 into coded buffer status
information, CSI, and E-TFRI. Because a CSI switch 1414 and a
buffer status switch 1416 are activated at a first time, they
switch the buffer status information and the CSI to a buffer status
channel decoder 1422 and a CSI channel decoder 1420,
respectively.
[0101] The buffer status channel decoder 1422 decodes the coded
buffer status information. A buffer status CRC checker 1426 checks
a CRC of the decoded buffer status information and provides a CRC
check result to a reception time controller 1434. The reception
time controller 1434 determines if the buffer status information
has been received from the UE. If the CRC check result is good,
which implies that the buffer status information has been received
from the UE, the reception time controller 1434 determines that it
is the first reception time and determines the reception time
points of the buffer status information and the CSI using
CNT.sub.sch.sub..sub.--.sub.int, T.sub.buffer, T.sub.CSI, and
THRES.sub.buffer. The reception time controller 1434 activates the
buffer status switch 1416 and the CSI switch 1414, respectively, at
the determined reception time points.
[0102] The CSI channel decoder 1420 channel-decodes the coded CSI.
An EUDCH scheduler 1430 generates scheduling assignment information
using the CSI received from the CSI channel decoder 1420 and the
buffer status information received from the buffer status CRC
checker 1426. The scheduling assignment information is transmitted
to the UE on the EU-SCHCCH. An E-TFRI channel decoder 1418
channel-decodes the coded E-TFRI received from the DEMUX 1412. An
E-TFRI CRC checker 1424 checks a CRC of the E-TFRI. If the CRC
check result is good, the E-TFRI is provided to an EUDCH data
decoder 1428. The EUDCH data decoder 1428 decodes EUDCH data
received on the EU-DPDCH from the UE using the E-TFRI.
[0103] A buffer status estimator 1432 estimates the buffer status
of the UE using the buffer status information and the E-TFRI. If
the buffer status estimate is less than THRES.sub.buffer, the
reception time controller 1434 concludes that it is time to
terminate the reception of the buffer status information and the
CSI, and controls an EU-SCHCCH transmitter (not shown) to transmit
a Scheduling Release message to the UE.
[0104] FIG. 15 is a flowchart illustrating a method for receiving
buffer status information and CSI in the Node B according to an
embodiment of the present invention. Referring to FIG. 15, the Node
B channel-decodes coded buffer status information received from the
UE in step 1500 and CRC-checks the decoded buffer status
information in step 1502. Using the CRC check result, the Node B
determines if the buffer status information has been received from
the UE in step 1504. If the CRC check is passed, the buffer status
information is provided to the EUDCH scheduler and the Node B goes
to step 1506. If the CRC check is failed, the Node B waits until
the next scheduling interval in step 1508 and returns to step
1500.
[0105] In step 1506, the Node B channel-decodes coded CSI following
the buffer status information and provides the decoded CSI to the
EUDCH scheduler. In step 1510, the Node B waits until the next
scheduling interval. The Node B estimates the buffer status of the
UE using the last received buffer status information and the amount
of received data in step 1512. An E-TFRI is known from the received
data amount and the buffer status is estimated by subtracting the
received data amount from the last received buffer status
information.
[0106] In step 1514, the Node B determines if the buffer status
estimate is equal to or greater than THRES.sub.buffer. If the
buffer status estimate is equal to or greater than
THRES.sub.buffer, the Node B proceeds to step 1516. However, if the
buffer status estimate is less than THRES.sub.buffer, the Node B
transmits a Scheduling Release message to the UE in step 1526, and
proceeds to step 1528. Step 1526 is marked with a dotted line to
indicate that it is optional. Without step 1526, the procedure
proceeds directly from step 1514 to step 1528. In step 1528, the
Node B determines whether to continue the EUDCH data service. If
the Node B determines to continue the EUDCH data service, it waits
until the next scheduling interval in step 1530 and returns to step
1500. However, if the Node B determines not to continue the EUDCH
data service, the procedure is terminated.
[0107] In step 1516, the Node B determines if the current
scheduling interval is a reception time of the buffer status
information. If it is, the Node B proceeds to step 1518. If it is
not, the Node B proceeds to step 1522. The Node B receives the
buffer status information in the current scheduling interval and
decodes it in step 1518, and CRC-checks the decoded buffer status
information in step 1520. If the CRC check is passed, the buffer
status information is provided to the EUDCH scheduler.
[0108] In step 1522, the Node B determines if the current
scheduling interval is a reception time of the CSI. If the current
scheduling interval is a reception time of the CSI, the Node B
receives the CSI in the current scheduling interval and decodes it
in step 1524. If the current scheduling interval is not a reception
time of the CSI, the Node B returns to step 1510.
[0109] FIG. 16 is a block diagram of an EU-SCHCCH receiver in the
UE, for receiving scheduling assignment information from the Node B
according to an embodiment of the present invention. Referring to
FIG. 16, an antenna 1600 receives an RF signal containing
scheduling assignment information from the UE. An RF processor 1602
downconverts the RF signal to a baseband signal. A pulse shaping
filter 1604 converts the baseband signal to a digital signal. A
descrambler 1606 descrambles the digital signal with the scrambling
code C.sub.scramble. The descrambled signal is provided to an
EU-SCHCCH channel decoder 1614 via a switch 1608, a despreader
1610, and a channel compensator 1612. The operation of the switch
1608 will be described later in more detail.
[0110] The EU-SCHCCH channel decoder 1614 channel-decodes a signal
received from the channel compensator 1612. An EU-SCHCCH CRC
checker 1616 CRC-checks the decoded EU-SCHCCH data to determine if
the scheduling assignment information has been received from the
Node B. If the CRC check is passed, the EU-SCHCCH CRC checker 1616
concludes that the decoded EU-SCHCCH data includes the scheduling
assignment information, detects the scheduling assignment
information, and provides it to a scheduling assignment reception
controller 1620. If the scheduling assignment information includes
a Scheduling Release message, the EU-SCHCCH CRC checker 1616
detects the Scheduling Release message and provides it to the
scheduling assignment reception controller 1620.
[0111] The scheduling assignment reception controller 1620 receives
buffer status information about the EUDCH data buffer,
THRES.sub.buffer, and a buffer status report flag. The buffer
status report flag is activated when the UE transmits the first
buffer status information to the Node B. Upon recognition from the
buffer status report flag that the first buffer status information
has been transmitted to the Node B, the scheduling assignment
reception controller 1620 activates the switch 1608 and receives
the scheduling assignment information from the Node B. The
scheduling assignment reception controller 1620 controls the switch
1608 using the buffer status information and THRES.sub.buffer. If
the buffer status information is equal to or greater than
THRES.sub.buffer, the switch 1608 is activated and receives the
scheduling assignment information. If the buffer status information
is less than THRES.sub.buffer, the switch 1608 is deactivated.
Additionally, upon receiving the Scheduling Release message from
the EU-SCHCCH CRC checker 1616, the scheduling assignment reception
controller 1620 deactivates the switch 1608.
[0112] FIG. 17 is a flowchart illustrating a method of the
EU-SCHCCH receiver in the UE according to an embodiment of the
present invention. Referring to FIG. 17, the UE determines if a
condition of initially receiving scheduling assignment information
has been satisfied in step 1700. The initial reception condition is
satisfied when the buffer status report flag is activated. If the
buffer status report flag is activated, the UE proceeds to step
1702. However, if the initial reception condition is not satisfied,
the UE waits until the next scheduling interval in step 1704.
[0113] The UE channel-decodes received EU-SCHCCH data in step 1702
and CRC-checks the decoded EU-SCHCCH data in step 1704. If the UE
determines by the CRC check that the decoded data is scheduling
assignment information in step 1708, it proceeds to step 1710.
However, if the decoded data is not scheduling assignment
information, i.e., the CRC check does not pass, the UE proceeds to
step 1712. The UE provides the scheduling assignment information to
the EUDCH transmission controller in step 1719, waits until the
next scheduling interval in step 1712, and proceeds to step
1714.
[0114] In step 1714, the UE monitors the state of the EUDCH data
buffer by comparing the amount of packet data stored in the EUDCH
data buffer with THRES.sub.buffer. According to the comparison
result, the UE determines whether to continue receiving the
scheduling assignment information in step 1716. Also, the UE makes
the determination by checking whether the scheduling assignment
information includes a Scheduling Release message. If the amount of
the packet data is equal to or greater than THRES.sub.buffer, or
the Scheduling Release message has not been received, the UE
returns to step 1702 to continue receiving the scheduling
assignment information. However, if the packet data amount is less
than THRES.sub.buffer or the Scheduling Release message has been
received, the UE determines whether to continue the EUDCH data
service in step 1718. If the UE determines to continue the EUDCH
data service, it waits until the next scheduling interval in step
1720 and returns to step 1700. If the UE determines to terminate
the EUDCH data service, it ends the procedure.
[0115] In accordance with the present invention as described above,
if the amount of data queued in a data buffer is equal to or
greater than a predetermined threshold, a UE transmits buffer
status information and CSI required for Node B control scheduling
at different intervals. The resulting decrease of signaling
overhead in transmitting uplink packet data leads to efficient use
of radio resources for an EUDCH mobile communication system.
[0116] While the present invention has been shown and described
with reference to certain preferred embodiments thereof, it will be
understood by those skilled in the art that various changes in form
and details may be made therein without departing from the spirit
and scope of the present invention as defined by the appended
claims.
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